High host density favors greater virulence: a model of parasite-host dynamics based on multi-type branching processes

We use a multitype continuous time Markov branching process model to describe the dynamics of the spread of parasites of two types that can mutate into each other in a common host population. While most mathematical models for the virulence of infectious diseases focus on the interplay between the dynamics of host populations and the optimal characteristics for the success of the pathogen, our model focuses on how pathogen characteristics may change at the start of an epidemic, before the density of susceptible hosts decline. We envisage animal husbandry situations where hosts are at very high density and epidemics are curtailed before host densities are much reduced. The use of three pathogen characteristics: lethality, transmissibility and mutability allows us to investigate the interplay of these in relation to host density. We provide some numerical illustrations and discuss the effects of the size of the enclosure containing the host population on the encounter rate in our model that plays the key role in determining what pathogen type will eventually prevail. We also present a multistage extension of the model to situations where there are several populations and parasites can be transmitted from one of them to another. We conclude that animal husbandry situations with high stock densities will lead to very rapid increases in virulence, where virulent strains are either more transmissible or favoured by mutation. Further the process is affected by the nature of the farm enclosures.

Improvements in glucose homeostasis in response to regular exercise are influenced by the PPARG Pro12Ala variant: results from the HERITAGE Family Study

AIMS/HYPOTHESIS

Exercise training improves glucose homeostasis, but large inter-individual differences are reported, suggesting a role of genetic factors. We investigated whether variants either confirmed or newly identified as diabetes susceptibility variants through genome-wide association studies (GWAS) modulate changes in phenotypes derived from an IVGTT in response to an endurance training programme.

METHODS

We analysed eight polymorphisms in seven type 2 diabetes genes (CDKAL1 rs7756992; CDKN2A and CDKN2B rs10811661 and rs564398; HHEX rs7923837; IGF2BP2 rs4402960; KCNJ11 rs5215; PPARG rs1801282; and TCF7L2 rs7903146) in a maximum of 481 sedentary, non-diabetic white individuals, who participated in a 20-week endurance training programme. Associations were tested between the variants and changes in IVGTT-derived phenotypes.

RESULTS

The only evidence of association with training response was found with PPARG rs1801282 (Pro12Ala). We observed that Ala carriers experienced greater increase in overall glucose tolerance (Deltaglucose disappearance index Ala/Ala 0.22 +/- 0.22, Pro/Ala 0.14 +/- 0.06, Pro/Pro 0.004 +/- 0.03; p = 0.0008), glucose effectiveness (Ala/Ala 0.28 +/- 0.41, Pro/Ala 0.44 +/- 0.14, Pro/Pro 0.09 +/- 0.06; p = 0.004), acute insulin response to glucose (Ala/Ala 64.21 +/- 37.73, Pro/Ala -11.92 +/- 40.30, Pro/Pro -46.30 +/- 14.70; p = 0.03) and disposition index (Ala/Ala 551.8 +/- 448.5, Pro/Ala 534.6 +/- 218.3, Pro/Pro -7.44 +/- 88.18; p = 0.003).

CONCLUSIONS/INTERPRETATION

Compared with Pro/Pro individuals, PPARG Ala carriers experienced greater improvements in glucose and insulin metabolism in response to regular endurance training. However, we did not find evidence of association between type 2 diabetes susceptibility variants recently identified through GWAS and glucose homeostasis response to exercise. Our results extend those of previous studies showing that Ala carriers appear to be more responsive to beneficial health effects of lifestyle interventions.

Correlation between blood pressure responses to dietary sodium and potassium intervention in a Chinese population

BACKGROUND

Blood pressure (BP) responses to dietary sodium and potassium intake vary among individuals. We examined the correlation between BP responses to dietary low-sodium, high-sodium, and potassium supplementation interventions in a feeding study.

METHODS

A total of 1,906 Chinese aged > or = 16 years participated in the dietary intervention that included a 7-day low-salt intervention (51.3 mmol/day), a 7-day high-salt intervention (307.8 mmol/day), and a 7-day high-salt plus potassium supplementation (60 mmol/day) intervention. BP was measured nine times during the 3-day baseline observation and during the last 3 days of each intervention phase using a random-zero sphygmomanometer.

RESULTS

The correlation coefficients (95% confidence intervals (CIs)) of the BP responses to low-sodium and high-sodium interventions were -0.47 (-0.51 to -0.44), -0.47 (-0.50 to -0.43), and -0.45 (-0.49 to -0.42) for systolic BP (SBP), diastolic BP (DBP), and mean arterial pressure (MAP), respectively (all P < 0.0001). The correlation coefficients (95% CI) of the BP responses to high-sodium intervention and potassium supplementation were -0.52 (-0.56 to -0.49), -0.48 (-0.52 to 0.45), and -0.52 (-0.55 to -0.48) for SBP, DBP, and MAP, respectively (all P < 0.0001). The kappa coefficients were moderate, varying from 0.28 to 0.34, between BP responses to low-sodium and high-sodium interventions (all P < 0.0001).

CONCLUSIONS

These results indicate there is a moderate correlation between BP responses to low-sodium and to high-sodium interventions, and BP responses to high-sodium intervention and potassium supplementation. Furthermore, our study suggests that individuals who were more sensitive to high-sodium diet might benefit more from a low-sodium and/or high-potassium intervention aimed at lowering BP levels.

The serial effects of multimodality therapy for stage III non-small cell carcinoma on lung function

7551

Purpose: To describe the effects of multimodality treatment on lung function in patients with stage III non-small cell carcinoma of the lung (NSCLC) Methods: Pulmonary function tests (PFTs) were reviewed for 32 patients with stage III NSCLC who were enrolled in a multimodality protocol that included neoadjuvant (NAd) combined chemoradiotherapy (taxol 50 mg/m2, carboplatin AUC 2 weekly X 3, radiation (XRT) 1.8 Gy BID to 30 Gy + erlotinib 150 mg/d for 28 days, followed by resection (R) and adjuvant (Ad) chemoradiotherapy (same as induction) followed by erlotinib 150mg/d maintenance (M) for 2 years. Changes in PFTs were analyzed at multiple time points (baseline to after NAd, after NAd to after R, after R to after Ad) and for the overall effect of treatment (baseline to the end of treatment). Results: The table below shows changes in percent predicted pulmonary function test values at each step in the treatment course. + signifies an increase and - a decrease. P indicates pneumonectomy and L lobectomy. Numbers in parentheses are the number of patients with complete testing at that time point. Conclusions: Neoadjuvant combined chemoradiotherapy has a small effect on lung function testing. The combined effect of multimodality therapy for stage III lung cancer that includes surgical resection leads to larger declines in lung function than have been reported historically for resection alone.

[Table: see text]

[Table: see text]

Variations in the four and a half LIM domains 1 gene (FHL1) are associated with fasting insulin and insulin sensitivity responses to regular exercise

AIMS/HYPOTHESIS

The expression of the four and a half LIM domains 1 gene (FHL1) is increased in the muscle of individuals who show an improvement in insulin sensitivity index (S(I)) after 20 weeks of exercise training. The aim of the present study was to investigate associations between three FHL1 single nucleotide polymorphisms (SNPs) and variables derived from an IVGTT, both in the sedentary state and in response to exercise training, in participants in the HERITAGE Family Study.

MATERIALS AND METHODS

SNPs were typed using fluorescence polarisation methodology. Analyses were performed separately by sex and in black and white individuals.

RESULTS

In black participants, no associations were found with any of the SNPs. In white women (n = 207), SNP rs9018 was associated with the disposition index (D(I)), which is calculated as S(I) generated from the MINMOD program (x10(-4) min(-1)[microU/ml](-1)) multiplied by acute insulin response to glucose (AIR(g); pmol/l x 10 min), and the glucose disappearance index (K(g)) training responses (p = 0.016 and p = 0.008, respectively). In white men (n = 222), all SNPs were associated with fasting glucose levels (p < or = 0.05) and SNP rs2180062 with the insulin sensitivity index (S(I)) (p = 0.04) in the sedentary state. Two SNPs were associated with fasting insulin training response. Fasting insulin decreased to a greater extent in carriers of the rs2180062 C allele (p = 0.01) and rs9018 T allele (p = 0.04). With exercise training, S(I) (x10(-4) min(-1)[microU/ml](-1): 0.68 +/- 0.20 vs -0.77 +/- 0.44, p = 0.046), D(I) (319 +/- 123 vs -528 +/- 260, p = 0.006) and K(g) (per 100 min: 0.09 +/- 0.04 vs -0.14 +/- 0.8, p = 0.03) improved more in the C allele carriers at rs2180062 than in the T allele carriers.

CONCLUSIONS/INTERPRETATION

Fasting insulin and S(I) responses to exercise training were associated with DNA sequence variation in FHL1 in white men. Whether these associations exist only in white men remains to be investigated.

Genome-wide scan to identify quantitative trait loci for baseline resting heart rate and its response to endurance exercise training: the HERITAGE Family Study

Evidence of a genetic component for resting heart rate (RHR) has been found. Quantitative trait loci (QTLs) for baseline RHR have been reported, but not for RHR training response. It is of interest to identify QTLs that may harbor genes influencing RHR variation at baseline and in response to regular exercise training. Here, a multipoint variance components linkage scan using 654 markers was performed to search for QTLs that influence RHR adjusted for several covariates at baseline and in response to 20 weeks of endurance training (post-training minus baseline) in 99 White and 127 Black families in the HERITAGE Family Study. Potentially interesting linkages were revealed on 4 q and 11 p for baseline RHR, and on 1 q and 21 q for RHR training response in Whites. The QTLs on 2 q, 6 q, 7 q, 12 q, 14 q, and 15 q for baseline RHR, and on 3 p, 20 p and 21 q for RHR training response were found in Blacks. Promising linkages (lod scores >or= 1.75, p <or= 0.0023) involved 11 p for baseline RHR in Whites and 3 p for RHR training response in Blacks, which did not replicate across races. Interestingly in this study, the linkage evidence on 11 p at the SUR locus was somewhat enhanced (lod score went up from 1.7 to 2.0) in a prehypertensive (BP >or= 135/80 mm Hg) subset of 40 White families suggesting a pleiotropic gene for BP and RHR with interactions. In conclusion, among QTLs on 1 q, 2 p, 3 p, 4 q, and 11 p that replicated across subsamples and studies, 11 p is most promising for dense mapping and association studies in HERITAGE and other cohorts.

The predictive value of baseline fluoro-deoxy-glucose positron emission tomography (FDG-PET) standardized uptake value (SUV) for overall survival in patients (pts) with locally advanced esophageal and gastroesophageal junction (GEJ) cancer

4062

Background: The predictive value of FDG-PET SUV in pts with esophageal and GEJ cancer has been subject of recent interest. The heterogeneity of disease stages and treatments made interpretation of reported data difficult.We evaluated the value of baseline FDG-PET SUV in a homogeneous patient (pt) population treated in a uniform fashion. Methods: Retrospective analysis of 71 pts with stages II-IVa esophageal and GEJ cancer treated on 2 phase 2 trials at the Cleveland Clinic Foundation. Data was collected on baseline pt and tumor characteristics, baseline SUV uptake, and outcomes. Results: All pts were treated with preoperative concurrent fluorouracil/cisplatin chemoradiotherapy (CRT); 69 pts proceeded to esophagectomy and 58 pts received additional postoperative adjuvant CRT. Median pt age was 60 (range 33–75) years, 86% were male, 89% had adenocarcinoma, 35%, 41% and 24% had stage II, III and IVa disease respectively. Pts have been followed for a median of 14 (range 3–50) months. All pts underwent a baseline FDG-PET scan with a mean primary site SUV of 8.9 (range 0–28.2). Pathological response (complete or partial) was achieved after induction CRT in 54% and was more likely in those with a baseline primary site SUV ≥ 7.3 (OR: 3.95, 1.43–10.9, P=0.008). Recurrence developed in 33 pts (46.5%) with distant metastases identified in 31 of these 33. The Kaplan-Meier 2-year projected overall survival for all 71 pts is 58% with a median of 31 months. Mortality was less in pts with baseline SUV ≥ 5.0 (HR: 0.44, 0.20–0.94, P = 0.033). After adjusting for clinical stage at diagnosis, tumor location and histology, baseline SUV ≥ 5 was still predictive of improved survival in multivariate analysis (HR: 0.35, 0.15–0.85, P = 0.02). Conclusions: In this retrospective analysis, esophageal and GEJ cancer pts with a higher baseline primary site SUV were more likely to respond to induction CRT and had better overall survival. This observation suggests that the subset of pts with more metabolically active tumor may derive greater benefit from multimodality treatments that include CRT. A prospectively designed trial would be required to confirm this hypothesis.

No significant financial relationships to disclose.

Genome-wide linkage scans for prediabetes phenotypes in response to 20 weeks of endurance exercise training in non-diabetic whites and blacks: the HERITAGE Family Study

AIMS/HYPOTHESIS

Impaired insulin secretion, insulin action, insulin-independent glucose effectiveness, glucose tolerance and the associated abnormalities in insulin and glucose metabolism phenotypes are precursors of type 2 diabetes. Genome-wide multipoint variance component linkage scans were carried out using 654 markers to identify quantitative trait loci for insulin sensitivity, acute insulin response to glucose, disposition index and glucose effectiveness training responses in whites and blacks in the HERITAGE Family Study.

METHODS

These phenotypes were obtained from an IVGTT with the minimal model. The distributions of insulin sensitivity, acute insulin response to glucose and disposition index training responses (post-training minus baseline) were approximately normalised using a square-root transformation. All phenotypes were adjusted for the effects of age, BMI and their respective baseline values within sex and generation by race prior to linkage scans.

RESULTS

In blacks, a promising linkage with a maximum lod score of 3.1 on 19q (54-62 Mb) for glucose effectiveness training response was found. Six interesting linkages with lod scores of at least 1.0 were found for disposition index training response in whites. They included 1p (30 Mb), 3q (152 Mb), 6p (23-42 Mb), 7q (95-96 Mb), 10p (15 Mb) and 12q (119-126 Mb).

CONCLUSIONS/INTERPRETATION

Quantitative trait loci for 20 weeks of endurance exercise training responses in insulin action and glucose metabolism phenotypes were found on chromosome 19q as well as 6p and 7q, with nominal (6p, 7q) but consistent (6p) linkages across the races.